Telephone system



March 5, 1940. m

TELEFHONB SYSTEM Filed Dec. 14, 19s;

' Patent ed Mor- Application December '14, 1938, semi No; 245,193

In ItalyDecember 2, 1938 p '1 Claims, (c1. 179-1) The present inventionhas 'for itsobject'an improvement in the systems 'of simultaneoustelephony on a number of lines.

According to the present invention there is provided telephonicapparatus adapted to be connected tothe normal local telephone lineswhich will receive and transmit simultaneous calls on a number of linesand furthermore permits convid ed, which permits thesuspending of aconnections to other lines which do not belong to the local network, forexample the internal linesof a factory or the like, engaged directly orthrough a manual or automatic party exchange. Further according to theinvention there is provided apparatus for simultaneous conversation on anumber of lines, wherein it is-possible to pass from a conversation bymeans of an ordinary microtelephone setto a conversation by means of amicrophone with elevated sensibility, situated at a certain distancefrom the person who uses the apparatus and by means of ,a loud speakerthrough an amplifier which is automatically included in the circuit.

According to this invention a device is proversation with one or morelines, although maintaining them busy, 'andto efiect simultaneouslydesired operation with the remaining lines, for instance calling one ormore of the remaining lines, leaving free one or more of said remaininglines, receiving an incoming call through one or more of said remaininglines, and finally reestablishing the suspended communication with theline or the lines first mentioned.

These'and other advantages. and possibilities will be obtained by meansofthe present inventionfwhichis illustrated in the accompanying drawingin one diagrammatic figure, which represents by example party telephoneequipment connected with two local lines and with three internal lines.

Referring to the drawing, the apparatus of the private set comprises theentrance conductors of two local or trunk' lines I and II, which areconnected respectively through normally closed keys A and A"'to completecircuits through condensers K and K" and relay coils R and R". The relaycoil R operates a group of contact springs l', 2', 3', l' and while therelay coil R" actuates contact springs l", 2", 3", 4" and 5". v

The springs I, I are designed to close a holding circuit for each of therelays R, R". The springs 2', 2" are provided for the purpose ofconnecting oneof the conductors of each line 'I, II with one of themovable contacts of the switch S through the dial D. The springs 3', 3-

D, and the conductor 20.

and the conductor have the object to connect the other conductor of eachof the lines I, II with the other of the The'sw'itch S is designed tobring the line or the lines I, II in connection with a normalmicrotelephone MT or with a device constituted by a group of microphonesM in series and an amplifier AM provided with a loudspeaker AL. v, Toone of the-contact springs 3, 3" there is connected a conductor CITwhich leads to a group of internal otlice telephone stations arranged inparallel which may be induced to oper ate by means of contacts 6, I, 8,by which the exit of the stations are: connected with earth. so A buzzerBU is connected with the conductor 9 and by means of a conductor Hi thiscircuit "ex tendsto the interrupters II, I 2 and IS, with the aid ofwhich-from the posts where are installed the inter-office stations MTI,MT2, MT3,th ere may be effected the call of the AL and MT respectively.

When there is an incoming ringing current through one of the two linesconnected with the principal post M,

'party set, for instance through the line I, the

relay R is energized closing at the same time 35.

all the contact springs I, 2', 3', 4' and 5'. The spring i thus closes aholding circuit forthe relay R" bridging the condenserK'. Thus when thealternating ringing current ceases, the relay R remains energized: 40The closing of the springs 2' connects the con-- ductor l6 of the line Iwith-the movable contact I! of theswitch S through the conductor 15,closed springs 2, conductor l8. conductor l9, dial The closing of thesprings 3' connects the conductor ll of line I with the contact 2l ofthe switch S throughthe interrupter A, the conductor 22, the springs 3',the conductor 23 and the conductor 24,

The closing of the springs 4 feeds the primary at volts, through thefollowing circuit; con-W ductor 25, springs 4"; the'prir'narywindingfZL-j 1- The closing of the springs energizes thelamp L throughthe following circuit: secondary winding 28 of the transformer 'IR,conductor 30, conductor 3|, lamp L', conductor 32, springs 5',conductor'33, conductor 34, and the winding 29.

Assuming the switch S to be in the position indicated in the drawing,the line I will thus be I extended to the contacts 35 and 36, with whichthere are connected, in parallel, the transformer TAM for the amplifierAM and-the microphone set M in series. The resistance offered by themicrophones in series and by the primary winding of the transformer TAMis substantially equal former TAM has the object to avoid reciprocalperturbing actions between the group of microphones. M and theloudspeaker AL.

The amplifier AM which is automatically placed in operation inconsequence of the energization of relay'R owing to the closing of thesprings 4' which close the feeding circuit of the primary winding of thetransformer I'm-may be of any suitable type, but as an example in thefollowing is described as an amplifier which in practice has given verygood results. It comprises two amplifying tubes TU I and TU2 each havinga filament with direct heating and rapid ignition.

One end of the secondary winding TAM is connected with the earth whilstthe other end is connected with the grid of the tube TUI and is furtherconnected with the earth through a resistance W, for instance of 500,000ohms. The anode of the tube TUI is connected through the condenser K2for example of the capacity of 50,000 fwith the first grid of the tubeTU2,

and through a resistance W2, for instance of 300,000 ohms with thesecondgrid of the tube T02. The anode of the tube TUZ-is connected tothe primary winding of the transformer TAL,

the secondary winding of which energizes the movable coil of theloudspeaker AL. The field coil FC of the loudspeaker AL is. fed by theconductors 31 and 38, arranged across an inductioncoil SC which isconnected in series between the second grid of the tube TU! and thecathode of the duo-diode DD. Two condensers K3 and- K4 disposed inseries are also connected across the coil SC and a point between thecondensers is grounded. The cathodes .of the tubes TUI and TU! are fedby the secondary windings 39 and .40 of the transformer TR, therespective electric centres of which are conducted to earth through thepolarized condensers K5 and KB. The duo-diode DD has the cathode thereoffed by the secondary winding 4| of the transformer TR and the anodes areconnected with the ends of the secondary winding 42 the electric centreof which is connected with the earth.

The incoming call, in accordance with what 1 -W'- in parallel on theline I, and the interrupter A' is then opened,- thus deenergizing therelayv coil R causing the opening of the spring contacts l 2', 3', 4'and 5'. If the operators closes for a short while the interrupter B'providing energization of the coil R" and therefore the closing of thegroup of springs I", 2", 3", 4", 5".- In such a way the line II isconnected "with instance has the value of 1,000 ohms.

Bymeans of the dial D the operator now calls the desired subscriberthrough the line II and after having received an answer, he closes theinterrupted B, energizing the coil R and causing the closing of thesprings I'-5' after which the switch 0' is opened.

The lines I and H are thus connected with the switch S. The circuit fromthe line I to A", the conductor 44, the contacts 3", the conductors 9and- 24, the switch S, the contact 20, the dial D, the conductors l9 and45, the contacts 2" and the conductors 46 and 41. The subscribers of thelines I, H and the station at M may now freely converse between eachother.

The operator of the station M can nowcall .into conference also one ormore of the interoiiice stations MTI, MT2, MT3, respectively by closingone or more of the interrupters 6, I, 8. In such a manner the operationof the buzzers BUI, BU2, BU3 is effected, which operation may beterminated by the called person opening the respective interrupters 50,5!, 52.

If it is desired to pass from the conversation by means of the set ofmicrophones M andthe loudspeaker AL a conversation bymeans of themicrotelephone MT, it will be sufficient to displace the movablecontacts l1 and 2| of the switch S from the position indicated in thedrawing to the contact position with the contacts 48 and 49. Theoperator of the station at M, AL may call one of the lines I and II, byfirst closing the interrupter B or 3'', thus energizing the coil R orR". Inthiswaythe springs l'-5' .or l"-5" connection with the desiredline. therefore effected in an of the dial D.

Thecallm By means of the closingof the respective interrupters. II, l2,I! each operatorwhich finds himself at one of the inter-ofiice telephonestations MTI, MT2, MT! may cause the operation of the buzzer BU, as aconsequence of which the ordinary way by, means" are closed, whereforethe station M, AL is in operator of thepriiicipal post M, AL, uponclosingthe corresponding interrupters 6, l, 8, places himself incommunicationwith the cailing'station. The operator of the inter-oflicestation perceives the reply of the operator of the princinumber, as wellas the internal lines.

2,192,540 pal post, hearing the buzzing of the respective buzzerBUi-BU3. Thereupon by opening the corresponding interrupter 50, Si or 52communication is established with the principal post.. Through theprincipal post the operator of the nected with the private party set M,AL, and

MT. It is obvious however that by means of a simple multiplication ofthe circuit elements, the local lines may be brought to whatsoeverdesired Therefore. each internal line may be provided with microphoneand loudspeaker, furnished with respective amplifiers for freeconversation. Applicant however does not confine himself to the exampleillustrated and described but declares that his invention has no otherlimits beyond those established in the following claims:

Having now particularly. described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is:

1. System of simultaneous telephony on a number of lines comprising incombination, entrance conductors for each line, a relay connected withsaid entrance conductors through a condenser, a holding circuit for.saidrelay controlled by the relay itself, groups of contact springscontrolled by said relays adapted to insert into the circuit of eachline a private party set, and a resistance provided with an interrupternormally opened connected in parallel with each of said lines in themanner and for the purposes described.

2. System of simultaneous telephony on a number of lines comprising incombination, entrance conductors for each line, a relay connected withsaid entrance conductors through a condenser, a holding circuit for thesaid relay controlled by the relay itself, groups of contact springscontrolled by the said relays adapted to insert in the circuit of eachline a private party set, a resistance provided with an interrupternormally opened connected in parallel with each of said lines, aninterrupter normally closed inserted between a conductor-of each of saidlines and the relay, and a second interrupter inserted'between thesecond conductor of each of the lines and said relay in parallel withthe condenser.

3. System of simultaneous automatic telephony on a number of linescomprising in combination, entrance conductors for each line, a relayconnected with said entrance conductors through a condenser, a holdingcircuit for the said relay controlled by the relay itself, groups ofcontact springs controlled by said relay adapted to insert in thecircuit of each line a private party set,

a resistance provided with an interrupter normallyopened connected inparallel with each of said lines, a microphone connected with said linesthrough contact springs operated by said relay, an amplifier connectedin parallel with said microphone, and a loudspeaker connected with saidamplifier.

4. System of simultaneous automatic telephony on a. number of linescomprising in combination, entrance conductors for each line, a relayconnected with said entrance conductors through a condenser, a holdingcircuit for said relay controlled by the relay itself, groups of contactsprings controlled by the relay adapted to insert in the circuit of eachline a private party set,

a resistance provided with aninterrupter normally opened connected inparallel with each of said lines, asupply transformer connected with thenetwork for an amplifier energized through contact springs controlled bysaid relay.

5. System of simultaneous automatic telephony on a number of linescomprising in combination, entrance conductors for each line, a relayconnected with said entrance conductors through a condenser, a holdingcircuit for said relay controlled by the relay itself, groups of contactsprings controlled by the relay adapted to insert in the circuit of eachline a private party set, a resistance provided with an interrupternormally opened connected in parallel with each of saidlines,-amicrophone and an amplifier, a number of internal telephonelines connected with said'microphone and said amplifier through a numberof interrupters.

6. System of simultaneous telephony on a number of lines comprising incombination, entrance conductors for each line, a relay connected withsaid entrance conductors through a condenser, a holding circuit for saidrelay controlled by the relay itself, groups of contact springscontrolled by said relay, adapted to insert in the circuit of each line.a private party set, a resistance provided with an interrupter normallyopened connected 'in parallel with each of said lines, a

switch for alternatively bringing into connection with said telephonelines a microphone and an amplifier in parallel between them and amicrotelephone respectively. a

7. System of simultaneous automatic telephony on a numberj of linescomprising in combination, entrance conductors for each line, a relayconnected with said entrance conductors through a condenser, a'holdingcircuit for said relay controlled by the relay itself, groups of contactsprings controlled by the relay adapted to insert in the circuit of eachline a private party set, a resistance provided with an interrupternormally openconnectedin parallel with each of said lines, a switch foralternatively bringing into connection with said telephone lines a setof microphones in series and an amplifier in parallel between them and amicrotelephone.

